Random Noise Influence On Spectrum Correcting Methods And Exactly Estimate Small Damping Of A Structure

The study is based on the project of National Natural Science Fund of China, the State Ministry of Education of China and State Key Laboratory of Vibration, Shock and Noise, which deeply research on spectrum correcting technology in dynamic signal analysis.When a signal contaminated by additive noise, the accuracy of the estimation of the parameters, i.e., amplitude, frequency and phase corrected by now existing four spectrum correcting methods will drop. This paper quantitatively investigates the noise influence on the accuracy of the universal-phase-difference-based method.This thesis also presents a new method for estimating the damping of a structure. The basic principle of this method is that sampling a length of continuous freedom transient responses signal, and performing FFT(Fast Fourier Transform) from the starting point, then shifting the starting point with L points and performing FFT again, finally estimating the damping by making use of the amplitudes of two corresponding peak lines. If not considering the model coupling, the method is a precise solution, and the estimating damping will not change with spectral leakage. The simulation results and engineering testing show that the estimated damping has high precise. The method can also apply to the Multi-DOF system.